Temperature sensor

Abstract

To provide a temperature sensor inhibited in variations of thermal characteristics.SOLUTION: A temperature sensor 1 comprises a thermistor element 2, a case 3, a case 4, and a resin 5. The thermistor element 2 includes a thermistor element assembly 21. The case 3 defines a space 30 accommodating the thermistor element assembly 21. The case 4 is located outside the case 3. The resin 5 is located in the space 30 and covers the thermistor element assembly 21. The case 3 includes a portion 31 and a portion 32. The portion 31 is covered by the case 4. The portion 32 is exposed from the case 4, and the thermistor element assembly 21 is located within the portion 32.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a temperature sensor. [Background technology]

[0002] A known temperature sensor includes a thermistor element including a thermistor body, and a resin portion that covers the thermistor element (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-19644 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one aspect of the present invention is to provide a temperature sensor in which variations in thermal characteristics are suppressed. [Means for solving the problem]

[0005] A temperature sensor according to one aspect of the present invention comprises a thermistor element, a first case, a second case, and a resin. The thermistor element includes a thermistor body. The first case defines a space that houses the thermistor body. The second case is located outside the first case. The resin is located within the space and covers the thermistor body. The first case includes a first portion and a second portion. The first portion is covered by the second case. The second portion is exposed from the second case, and the thermistor body is located inside.

[0006] In the one aspect above, the thermistor element is housed in the space of the first case and covered with resin. Since the thermistor element is housed in the space of the first case, it is located toward the inside of the temperature sensor by at least the thickness of the first case. Compared to a temperature sensor that does not have a first case, in the one aspect above, variation in the position of the thermistor element in the temperature sensor is suppressed. Therefore, when the temperature sensor is placed on the object to be measured, variation in the distance from the object to be measured to the thermistor element is suppressed. As a result, variation in the amount of heat transferred from the object to be measured to the thermistor element is suppressed, and therefore variation in the thermal characteristics of the temperature sensor is suppressed. Effect of the Invention

[0007] One aspect of the present invention provides a temperature sensor having reduced variations in thermal characteristics. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of a temperature sensor according to an embodiment. [Diagram 2] FIG. 2 is a perspective view of the first case according to the present embodiment. [Diagram 3] FIG. 3 is a perspective view of the first case according to the present embodiment. [Figure 4] FIG. 4 is a diagram showing a cross-sectional configuration of the temperature sensor according to this embodiment. [Diagram 5] FIG. 5 is a diagram showing a cross-sectional configuration of the temperature sensor according to this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and duplicated descriptions will be omitted as appropriate.

[0010] The configuration of the temperature sensor according to the present embodiment will be described with reference to Figs. 1 to 5. Fig. 1 is a perspective view of the temperature sensor according to the present embodiment. Fig. 2 is a perspective view of a first case according to the present embodiment. Fig. 3 is a perspective view of the first case according to the present embodiment in a different direction from that of Fig. 2. Fig. 4 is a diagram showing the cross-sectional configuration of the temperature sensor according to the present embodiment. Fig. 5 is a diagram showing the cross-sectional configuration of the temperature sensor according to the present embodiment in a different direction from that of Fig. 4.

[0011] 1 and 5, the temperature sensor 1 includes a thermistor element 2, a case 3, a case 4, a resin 5, and a wire 6. For example, the case 3 is defined as a first case, and the case 4 is defined as a second case. In one example, the temperature sensor 1 is used as a sensor for measuring the temperature of a liquid.

[0012] 4 and 5, the thermistor element 2 has a thermistor body 21, a sealing body 22, and conductive wires 23. The thermistor element 2 is an electronic component whose resistance value changes in response to an increase in temperature. The thermistor body 21 may include an NTC (Negative Temperature Coefficient) thermistor and a PTC (Positive Temperature Coefficient) thermistor. The thermistor body 21 constitutes a detection unit whose resistance value changes in response to a change in temperature.

[0013] The encapsulant 22 encapsulates the thermistor element 21 inside. The thermistor element 21 is covered by the encapsulant 22. In one example, the encapsulant 22 includes glass directly covering the thermistor element 21 and a coating agent covering the glass. The conductor 23 includes a conductor 23a and a conductor 23b. The conductor 23a and the conductor 23b are electrically connected to two electrodes provided on the thermistor element 21, respectively. For example, the conductor 23a and the conductor 23b are connected to the two electrodes, respectively, by a conductive bonding material. Each of the conductors 23a and 23b includes a dumet wire sealed in the encapsulant 22 together with the thermistor element 21 and a lead wire exposed from the encapsulant 22.

[0014] The case 3 defines a space 30 that houses the thermistor body 21. The space 30 is defined on an inner peripheral surface 30a of the case 3. In this embodiment, the case 3 has a bottomed cylindrical shape. The space 30 corresponds to a hole in the bottomed cylindrical shape. The case 3 includes an end 3b in which an opening 3a communicating with the space 30 is formed. In this embodiment, the opening 3a and the inner peripheral surface 30a have an elliptical shape when viewed from a direction D1 perpendicular to the opening 3a. When viewed from the direction D1, the opening 3a and the inner peripheral surface 30a may have a perfect circular shape, an elliptical shape, or a polygonal shape. The space 30 extends along the direction D1. The direction D1 is the longitudinal direction of the case 3.

[0015] In this embodiment, the width of the space 30 is constant from the position where the thermistor body 21 is accommodated to the opening 3a. The width of the space 30 is the inner diameter of the case 3 along a direction perpendicular to the direction D1. The width a1 shown in FIG. 4 is the inner diameter of the case 3 along a direction D2, which is one of the directions perpendicular to the direction D1. The width a1 of the space 30 is constant from the position where the thermistor body 21 is accommodated to the opening 3a. The width b1 shown in FIG. 5 is the inner diameter of the case 3 along a direction D3 perpendicular to the directions D1 and D2. The width b1 of the space 30 is constant from the position where the thermistor body 21 is accommodated to the opening 3a.

[0016] The thermistor body 21 is housed in the space 30. The resin 5 is located in the space 30 and covers the thermistor body 21. In this embodiment, the resin 5 indirectly covers the thermistor body 21 via the sealing body 22. In one example, the resin 5 is an epoxy resin that is filled in the space 30 and then hardened. The thermistor element 2 is embedded in the resin 5.

[0017] Case 4 is located outside case 3. Case 4 covers a part of case 3. Case 3 includes a portion 31 that is covered by case 4 and a portion 32 that is exposed from case 4. For example, portion 31 is defined as a first portion, and portion 32 is defined as a second portion. Portion 31 and portion 32 are adjacent to each other in direction D1.

[0018] The portion 32 is exposed from the case 4 and corresponds to a position of the space 30 that accommodates the thermistor element 21. The portion 32 includes the bottom surface of the case 3. The thermistor element 21 is located inside the portion 32. In one example, the temperature sensor 1 is used such that the portion 32 is immersed in a liquid.

[0019] As shown in FIG. 2 and FIG. 3, the portion 31 includes a cylindrical portion 31a and a cylindrical portion 31b. The cylindrical portion 31a and the portion 32 are adjacent to each other in the direction D1. The cylindrical portion 31b and the cylindrical portion 31a are adjacent to each other in the direction D1. The portion 31, the cylindrical portion 31a, and the cylindrical portion 31b are arranged in the order of the portion 31, the cylindrical portion 31a, and the cylindrical portion 31b. In this embodiment, the cylindrical portion 31a has a cylindrical shape. The cylindrical portion 31a is not limited to a cylindrical shape. The flange portion 3c is located between the portion 32 and the cylindrical portion 31a. The flange portion 3c protrudes in a direction perpendicular to the direction D1 and extends in an annular shape. The flange portion 3d is located between the cylindrical portion 31a and the cylindrical portion 31b. The flange portion 3d protrudes in a direction perpendicular to the direction D1 and extends in an annular shape.

[0020] In this embodiment, the cylindrical portion 31b has a rectangular shape when viewed from the direction D1. The shape of the cylindrical portion 31b when viewed from the direction D1 is not limited to a rectangular shape. The cylindrical portion 31b includes a pair of side surfaces facing each other in the direction D2 and a pair of side surfaces facing each other in the direction D3. The end 3b is an end of the cylindrical portion 31b in the direction D1. A pair of protrusions 3e protrude along the direction D3 from a pair of imaginary planes including the pair of side surfaces of the cylindrical portion 31b facing each other along the direction D3. A V-shaped groove extending along the direction D1 is formed in each of the protrusions 3e. A pair of openings 42c are formed in the case 4. Each of the V-shaped grooves of the pair of protrusions 3e is exposed from the pair of openings 42c.

[0021] The case 3 includes a portion 33. For example, the portion 33 is defined as a third portion. The portion 33 is continuous with the end 3b and extends from the end 3b in a direction intersecting the direction D1. In this embodiment, the portion 33 extends along the direction D3 and protrudes along the direction D3. A pair of grooves 33x are formed in the portion 33. Each groove 33x opens in the direction D1 and extends along the direction D3.

[0022] The wire 6 is electrically connected to the thermistor element 2. In one example, the wire 6 is connected to the conductor 23 by a crimping member (not shown). The wire 6 is, for example, a coated electric wire. The wire 6 has a wire 61 and a wire 62. The wire 61 and the wire 62 are electrically connected to the conductor 23a and the conductor 23b, respectively.

[0023] As shown in FIG. 5, the wire 6 includes a wire portion 6a, a wire portion 6b, and a wire portion 6c. For example, the wire portion 6a is defined as a first wire portion, the wire portion 6b is defined as a second wire portion, and the wire portion 6c is defined as a third wire portion. The wire portion 6a is located in the space 30. The wire portion 6a is connected to the thermistor element 2. The wire portion 6b extends along the portion 33. In this embodiment, the wire portion 6b is disposed in the groove 33x. The wire portion 6c is a portion that is continuous with the wire portion 6a and the wire portion 6b. The wire portion 6c is located between the wire portion 6a and the wire portion 6b, and is curved.

[0024] 2 and 3, the portion 33 includes a bottom surface 33a and a pair of inner surfaces 33b that define a groove 33x. The bottom surface 33a defines the bottom of the groove 33x. The pair of inner surfaces 33b face each other in a direction D2. The pair of inner surfaces 33b includes a region 33s and a region 33t. For example, the region 33s is defined as a first region, and the region 33t is defined as a second region.

[0025] In the region 33s, the pair of inner surfaces 33b are spaced apart by an interval equal to or greater than the maximum width of the wire portion 6b. In this embodiment, the pair of inner surfaces 33b are spaced apart by an interval greater than the diameter of the wire portion 6b in the region 33s. The region 33s and the bottom surface 33a are adjacent to each other. The region 33t is farther from the bottom surface 33a than the region 33s, and is farther from the bottom surface 33a than the portion of the wire portion 6b having the maximum width. In this embodiment, the region 33t is farther from the bottom surface 33a than the diameter of the wire portion 6b. In the region 33t, the pair of inner surfaces 33b are spaced apart by an interval smaller than the diameter of the wire portion 6b. The wire portion 6b is disposed so as to be adjacent to the region 33s in the direction D2 and to be located between the bottom surface 33a and the region 33t in the direction D1.

[0026] As shown in FIG. 1, the case 4 includes a portion 41 and a portion 42. The portion 41 covers the cylindrical portion 31a. The portion 42 covers the cylindrical portion 31b. The portion 41 and the portion 42 are adjacent to each other in the direction D1. The portion 41 has a cylindrical shape with the direction D1 as the central axis and a direction perpendicular to the direction D1 as the radial direction. The portion 42 has a hollow, approximately rectangular parallelepiped shape including a pair of side surfaces facing each other along the direction D2 and a pair of side surfaces facing each other along the direction D3. A space in which the case 3 is located is formed inside the portion 42. In this embodiment, the case 4 covers the opening 3a, the end 3b, a part of the wire portion 6a, the wire portion 6b, the wire portion 6c, and the groove 33x.

[0027] The portion 41 includes a portion 41a, a portion 41b, and a portion 41c. The portion 41b is located between the portion 41a and the portion 41c. The portions 41a, 41b, and 41c are aligned along the direction D1. The diameter of the portion 41b is smaller than the diameters of the portions 41a and 41c. The portions 41a, 41b, and 41c form a groove whose bottom surface is the surface of the portion 41b.

[0028] The portion 33 includes an end face 33c exposed from the case 4. For example, the end face 33c is defined as a first end face. The end face 33c is exposed from the portion 42. The case 4 includes the end face 33c and a flat end face 42a. The end face 42a is included in the portion 42. For example, the end face 42a is defined as a second end face. The end face 33c and the end face 42a are located on the same imaginary plane. In this embodiment, the end face 33c and the end face 42a are perpendicular to the direction D3. The end face 33c and the end face 42a include an edge that defines an opening 3f in which the wire portion 6b is located. The wire portion 6b is inserted into the opening 3f.

[0029] The portion 33 includes an end face 33d exposed from the case 4. The end face 33d is exposed from the portion 42. The case 4 includes the end face 33d and a flat end face 42b. The end face 42b is included in the portion 42. The end face 33d and the end face 42b are located on the same imaginary plane. In this embodiment, the end face 33d and the end face 42b are perpendicular to the direction D1.

[0030] The case 3 and the case 4 are made of a resin material. The case 3 and the case 4 may be made of a PPS (polyphenylene sulfide) resin, a PBT (polybutylene terephthalate) resin, or a PA (polyamide) resin. In another embodiment, the case 3 and the case 4 may be made of different resin materials.

[0031] With the thermistor element 2, wire 6, and resin 5 arranged in the space 30 of the case 3, the case 3 is insert-molded into the case 4. In the mold for molding the case 4, the end face 33d of the case 3 is abutted against the inner surface of the mold, and a positioning member is inserted into each of the V-shaped grooves of the pair of protrusions 3e, thereby positioning the case 3.

[0032] As described above, the thermistor element 21 is housed in the space 30 of the case 3 and is covered with the resin 5. Since the thermistor element 21 is housed in the space 30 of the case 3, it is located toward the inside of the temperature sensor 1 by at least the thickness of the case 3. Compared to a temperature sensor not having a case 3, the temperature sensor 1 reduces the variation in the position of the thermistor element 21 in the temperature sensor. Therefore, when the temperature sensor 1 is placed on an object to be measured, the variation in the distance from the object to the thermistor element 21 is reduced. As a result, the variation in the amount of heat transferred from the object to be measured to the thermistor element 21 is reduced, and the variation in the thermal characteristics of the temperature sensor 1 is reduced. Therefore, the temperature sensor 1 provides a temperature sensor with reduced variation in thermal characteristics.

[0033] The temperature sensor 1 includes a wire 6 electrically connected to the thermistor element 2. The case 3 is continuous with an end 3b at which an opening 3a communicating with the space 30 is formed, and includes a portion 33 extending from the end 3b in a direction intersecting the direction D1. The wire 6 includes a wire portion 6a, a wire portion 6b, and a wire portion 6c. The wire portion 6a is located within the space 30. The wire portion 6b is along the portion 33. The wire portion 6c is located between the wire portions 6a and 6b, and is curved. Wire portion 6a is fixed to case 3 by resin 5, and wire portion 6b is positioned at portion 33 of case 3. Therefore, wire portion 6c located between wire portion 6a and wire portion 6b is likely to maintain a curved shape. When wire portion 6c maintains a curved shape, wire portion 6c is less likely to deform, for example, bend. As a result, wire 6 is less likely to break. In this embodiment, the wire portion 6c is covered by the case 4. Therefore, when the temperature sensor 1 is used, the wire portion 6c is protected by the case 4. As a result, the wire portion 6c is even less likely to deform or break.

[0034] A groove 33x is formed in the portion 33. The wire portion 6b is disposed in the groove 33x. In the temperature sensor 1, since the wire portion 6b is disposed in the groove 33x, the wire portion 6b is unlikely to deviate from the portion 33. Therefore, the variation in the position of the wire portion 6c is suppressed, and the wire portion 6c is more likely to maintain the curved shape.

[0035] The portion 33 includes a bottom surface 33a and a pair of inner surfaces 33b. The bottom surface 33a defines the bottom of the groove 33x. The pair of inner surfaces 33b, together with the bottom surface 33a, define the groove 33x and face each other. The pair of inner surfaces 33b includes a region 33s and a region 33t. The region 33t is farther from the bottom surface 33a than the region 33s, and is farther from the bottom surface 33a than the portion of the wire portion 6b having the maximum width. In the region 33s, the pair of inner surfaces 33b are spaced apart by a distance equal to or greater than the maximum width. In the region 33t, the pair of inner surfaces 33b are spaced apart by a distance smaller than the maximum width. In the temperature sensor 1, the wire portion 6b arranged in the groove 33x is located adjacent to the region 33s. When the wire portion 6b moves in a direction to come out of the groove 33x, the wire portion 6b interferes with the region 33t. Therefore, the wire portion 6b is difficult to come out of the groove 33x. As a result, the wire portion 6c is more likely to maintain the curved shape.

[0036] The portion 33 includes an end face 33c exposed from the case 4. The case 4 includes the end face 33c and a flat end face 42a. The end face 33c and the end face 42a include an edge that defines an opening 3f in which the wire portion 6b is located. In the temperature sensor 1, the end face 33c and the end face 42a are flat with each other, so that the wire portion 6b is unlikely to interfere with areas other than the edge of the opening 3f.

[0037] 3. The temperature sensor according to claim 2, wherein widths a1, b1 of the space (30) are constant from the position housing the thermistor body (21) to the opening (3a). The temperature sensor 1 can reduce variation in the position of the thermistor element body 21 compared to a configuration in which the widths a1, b1 of the space 30 are not constant. Therefore, when the temperature sensor 1 is placed on an object to be measured, variation in the distance from the object to be measured to the thermistor element body 21 is further reduced.

[0038] The cases 3 and 4 are made of a resin material. Resin materials are easier to mold than, for example, metal materials, etc. Therefore, in the temperature sensor 1, by making the case 4 out of a resin material, a configuration in which the case 4 covers the case 3 can be easily realized. Since both cases 3 and 4 are made of a resin material, the difference in the thermal expansion coefficients of cases 3 and 4 is smaller than in a configuration in which cases 3 and 4 are made of different materials. Therefore, a gap is unlikely to occur between cases 3 and 4. As a result, temperature sensor 1 improves the durability of the temperature sensor.

[0039] The present invention has been described in detail above based on the embodiments. However, the present invention is not limited to the above embodiments. The present invention can be modified in various ways without departing from the spirit and scope of the present invention.

[0040] The portion 31 does not have to be directly covered by the case 4. Another member may be interposed between the case 4 and the portion 31. The portion 31 may be indirectly covered by the case 4. The pair of inner surfaces 33b may not include the regions 33s and 33t. In the configuration in which the pair of inner surfaces 33b include the regions 33s and 33t, as described above, the wire portion 6c can more easily maintain the curved shape. The groove 33x may not be formed in the portion 33. In the configuration in which the groove 33x is formed in the portion 33, the wire portion 6b is unlikely to deviate from the portion 33, as described above. The end face 42a does not have to be flat on the end face 33c. A step may be formed between the end face 42a and the end face 33c. In the configuration in which the end face 42a is flat on the end face 33c, as described above, the wire portion 6b is unlikely to interfere with the area other than the edge of the opening 3f. The width of the space 30 does not have to be constant from the position housing the thermistor element 21 to the opening 3a. The width of the space 30 may increase from the position housing the thermistor element 21 toward the opening 3a. In a configuration in which the width of the space 30 increases from the position housing the thermistor element 21 toward the opening 3a, the thermistor element 21 is easily accommodated within the space 30.

[0041] As will be understood from the description of the above embodiments, the present specification includes disclosure of the following aspects. (Appendix 1) a thermistor element including a thermistor body; a first case defining a space for accommodating the thermistor element; a second case located outside the first case; a resin located within the space and covering the thermistor body, The first case is A first portion covered by the second case; a second portion exposed from the second case and corresponding to a position in the space that houses the thermistor element. (Appendix 2) The thermistor element further includes a wire electrically connected to the thermistor element. the first case includes a third portion that is continuous with an end where an opening communicating with the space is formed and that extends from the end in a direction intersecting with a direction in which the space extends, The wire is a first wire portion located within the space; a second wire portion along the third portion; and a third wire portion located between the first wire portion and the second wire portion and curved. (Appendix 3) The third portion has a groove formed therein, 3. The temperature sensor of claim 2, wherein the second wire portion is disposed in the groove. (Appendix 4) The third portion is a bottom surface defining a bottom of the groove; a pair of opposing inner surfaces defining the groove together with the bottom surface; The pair of inner surfaces are A first region; a second region that is farther from the bottom surface than the first region and farther from the bottom surface than a portion of the second wire portion having a maximum width, In the first region, the pair of inner surfaces are spaced apart by a distance equal to or greater than the maximum width, 4. The temperature sensor of claim 3, wherein in the second region, the pair of inner surfaces are spaced apart by a distance smaller than the maximum width. (Appendix 5) the third portion includes a first end surface exposed from the second case, the second case includes the first end surface and a flat second end surface; The temperature sensor according to any one of claims 2 to 4, wherein the first end surface and the second end surface include edges that define an opening in which the second wire portion is located. (Appendix 6) 6. The temperature sensor according to claim 2, wherein a width of the space is constant from the position housing the thermistor body to the opening. (Appendix 7) 7. The temperature sensor according to claim 1, wherein the first case and the second case are made of a resin material. [Explanation of symbols]

[0042] 1...temperature sensor, 2...thermistor element, 21...thermistor body, 3...case, 3a...opening, 3b...end, 30...space, 31, 32, 33...portion, 33a...bottom surface, 33b...pair of inner surfaces, 33c...end surface, 33x...groove, 33s, 33t...area, 4...case, 42a...end surface, 5...resin, 6...wire, 6a, 6b, 6c...wire portion, a1, b1...width, D1, D2, D3...direction.

Claims

1. a thermistor element including a thermistor body; a first case defining a space for accommodating the thermistor element; a second case located outside the first case; a resin located within the space and covering the thermistor body, The first case is A first portion covered by the second case; a second portion exposed from the second case and corresponding to a position in the space that houses the thermistor element.

2. The thermistor element further includes a wire electrically connected to the thermistor element. the first case includes a third portion that is continuous with an end where an opening communicating with the space is formed and that extends from the end in a direction intersecting with a direction in which the space extends, The wire is a first wire portion located within the space; a second wire portion along the third portion; 2. The temperature sensor of claim 1, further comprising a third wire portion located between the first wire portion and the second wire portion and being curved.

3. The third portion has a groove formed therein, The temperature sensor of claim 2 , wherein the second wire portion is disposed within the groove.

4. The third portion is a bottom surface defining a bottom of the groove; a pair of opposing inner surfaces defining the groove together with the bottom surface; The pair of inner surfaces are A first region; a second region that is farther from the bottom surface than the first region and farther from the bottom surface than a portion of the second wire portion having a maximum width, In the first region, the pair of inner surfaces are spaced apart by a distance equal to or greater than the maximum width, The temperature sensor according to claim 3 , wherein in the second region, the pair of inner faces are spaced apart by a distance smaller than the maximum width.

5. the third portion includes a first end surface exposed from the second case, the second case includes the first end surface and a flat second end surface; The temperature sensor of claim 2 , wherein the first end surface and the second end surface include edges defining an opening in which the second wire portion is located.

6. 5. The temperature sensor according to claim 2, wherein a width of the space is constant from the position housing the thermistor body to the opening.

7. The temperature sensor according to claim 1, wherein the first case and the second case are made of a resin material.

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